The invention relates to an auxiliary planet-wheel gear for motor vehicles of the type in which a drive drum fixed in terms of rotation relative to an outer central wheel, a shift sleeve connecting an inner central wheel to a brake located outside the drive drum, and an intermediate drive shaft fixed in terms of rotation relative to a planet carrier are arranged concentrically relative to one another.
In a known auxiliary gear of this type (German Published Unexamined Patent Application (DOS) No. 2,801,812), the drive drum is supported at its end facing the brake relative to the shift sleeve by means of a roller bearing and, at its other end, relative to the intermediate drive shaft, by means of a roller bearing, so that the two central wheels and the planet carrier are arranged in the interior enclosed by the two roller bearings. This known auxiliary gear has a construction which is long in the direction of the main gear axis, because the roller bearings used for support relative to the intermediate drive shaft, the set of planet wheels, the roller bearings used for support relative to the shift sleeve, and an annular seal arrangement inserted between the drive drum and shift sleeve are arranged axially behind one another.
A further known auxiliary planet-wheel gear of a similar type described in U.S. Pat. No. 3,469,473 has an even longer construction, because, in this arrangement, on the one hand the brake connected to the shift sleeve is located in the drive drum, and on the other hand the drive drum roller bearing used for support relative to the intermediate drive shaft is located on the side of the central wheels which is opposite the brake.
Finally, the disadvantage of a long construction is also inherent in known auxiliary planet-wheel gears of a different generic type (see German Published Unexamined Patent Application -DOS- No. 3,103,397 and above-noted U.S. Pat. No. 2,943,517), because in these arrangements the drive drum or a gear member used in an appropriate way as a gear output member each require, likewise, two roller bearings located on both sides of the central wheels.
An object on which the invention is based is primarily to achieve a short overall length in an auxiliary planet-wheel gear of the generic type. This object is achieved according to preferred embodiments of the invention by providing that the drive drum has only a single roller bearing which, together with an associated bearing extension of the planet carrier, is offset in the direction of the brake in relation to the central wheels.
In especially preferred embodiments of the invention, with reference to the main gear axis, the radially outer drive drum and the shift sleeve are each supported relative to the centrally arranged intermediate drive shaft by roller bearings with the roller bearing of the shift sleeve being arranged offset in the direction of the brake in relation to the central wheels. Further, the planet carrier is converted to an annular bearing extension supporting the roller bearing of the drive drum.
According to another aspect of preferred embodiments of the invention, the single roller bearing of the drive drum is arranged concentrically on the outside relative to the roller bearing of the shift sleeve.
According to another aspect of preferred embodiments of the invention, the bearing extension projects beyond a seal arrangement inserted between the drive drum and shift sleeve.
According to another aspect of preferred embodiments of the invention, the planet carrier has a hub for connecting it fixedly in terms of rotation to the intermediate drive shaft, and two radial annular webs for retaining planet bolts, one annular web of which is provided with the bearing extension, characterized in that the bearing extension is connected to the annular web facing the brake and the other annular web is connected by means of a conical hub part to the hub arranged axially offset in the direction of the brake in relation to the central wheels.
According to another aspect of preferred embodiments of the invention, the roller bearing of the shift sleeve is a ball bearing.
According to another aspect of preferred embodiments of the invention there is provided a flow guide device which projects into an annular space between the annular web facing the brake and the gasket arrangement inserted between the drive drum and shift sleeve, which flow guide device is arranged fixedly in terms of movement relative to the shift sleeve and scoops lubricant from the annular space and conveys it through a free-wheel coupling into a shaft channel of the intermediate drive shaft, and wherein the free-wheel coupling is located next to the roller bearing of the shift sleeve, characterized in that the roller bearing of the shift sleeve is located in the flow path between the flow guide device and the free-wheel coupling.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawing which shows, for purposes of illustration only, an embodiment constructed in accordance with the present invention.